This invention relates to an industrial robot of the horizontal multi-articulation type wherein a second arm is mounted for pivotal motion about a vertical axis at an end of a first arm which is in turn mounted at the other end thereof for pivotal motion about another vertical axis at a stationary member.
A typical one of industrial robots of the type described above is disclosed, for example, in Japanese Laid-Open Utility Model No. 57-186289. In this arrangement, a speed reduction gear is fitted around an input power shaft by way of a speed reduction gear securing block, and a housing secured to a second arm is provided around the speed reduction gear and is fitted between upper and lower projections at an end of the first arm. Accordingly, in assembling operations of the second arm of the arrangement, the housing which is integral with the second arm and in which the speed reduction gear is incorporated is first fitted laterally into the end portion of the first arm, and then the input power shaft is inserted into the housing and is fitted in the speed reduction gear whereafter a pulley is fitted on the input power shaft and a belt is mounted on the pulley. In this way, very complicated and time consuming operations are required for such mounting and adjustment. In addition, for example, when the second arm is to be removed due to a trouble to or for adjustment of the speed reduction gear and so on, the belt must be first removed reversely and the input power shaft must then be pulled off before removal of the second arm. Thus, the conventional arrangement has several defects in structure principally for assembling of the same.